1. Field of the Invention
This invention relates to fabricated tubular truss and frame structures, and in particular to structures assembled using carbon-fiber tubes or rods.
2. Description of Related Art
Trusses and frame type structures have been used for many years as an efficient method to create lightweight, yet extremely stiff support structures. Trusses are particularly useful when a load must be carried over long distances, such as in building roofs, bridges, and cranes.
Prior art exists for various types of truss connector systems. U.S. Pat. No. 435,156 (Schmemann) discloses a design for an arch pipe truss for use in roofs. Schmemann uses rod members with threaded ends, which are threaded in joint connectors with mating receptacles. This design, however, does not allow the user to select the angle for the diagonal arbitrarily.
U.S. Pat. No. 2,487,169 (Newell) discloses a joint connector used for creating pipe trusses. This connector is fabricated by intersecting plates fitted axially into the pipe end. This joint must be welded together, especially for each individual joint.
U.S. Pat. No. 3,985,459 (Gilb) discloses a ridge joint connector assembly. In this joint, two pairs of sheet metal fastener plates are placed on the inside and outside faces of the ends of lumber members. This joint does not allow for the connection of tubes and rods, nor does it permit the connection of members orthogonal to the first two members. U.S. Pat. No. 4,050,210 (Gilb) also discloses a ridge connector for light composite trusses composed of lumber top chords and metal webs. Here, pairs of U-shaped connectors are used, along with pins and slots to hold the members together.
U.S. Pat. No. 4,161,088 (Gugliotta) discloses a pipe-and-ball truss array for supporting deck surfaces. This joint includes a spherically shaped joint center, with tubular members bolted to various locations on the sphere. U.S. Pat. No. 4,915,533 (De la Haye) discloses a coupling piece for joining two or more rods. This patent uses a round or polygonal shaped piece, into which the rods are bolted at specific locations. U.S. Pat. No. 5,310,273 (Hara) discloses a joint structure for removably attaching a ball member to an end of a bar to form a truss structure, which engages using a tension rod.
U.S. Pat. No. 4,650,361 (Seuster) discloses a joint for truss structures including fiber composite material. In particular, the joint attaches reflector panels in a truss support structure for a radio telescope, and the truss bars and reflector panels are made from carbon-fiber composites. Here, the joint includes a ball into which bolts are fastened, with the ends attached to the fiber composite bars.
U.S. Pat. No. 3,229,998 (Pennington), U.S. Pat. No. 4,667,505 (Sharp), U.S. Pat. No. 4,870,856 (Sharp), U.S. Pat. No. 4,840,201 (Botsolas), U.S. Pat. No. 5,007,666 (Kyfes), and U.S. Design Pat. No. D362,916 (Cetrulo) disclose various types of split or clam-shell shaped joiners. These methods, however, do not incorporate means to connect diagonal connectors, and hence cannot be used exclusively to form a truss structure. Similarly, U.S. Pat. No. 6,032,430 (Soukup), U.S. Pat. No. 5,346,237 (Wang), U.S. Pat. No. 6,604,710 (Ohmer), and U.S. Pat. No. 5,711,131 (Thomas) all disclose connection methods for bars; however, in each case the directions of the individual members is predetermined by the specific connector. That is, the user needs multiple types of connectors to fabricate an entire structure with multiple internal angles.
U.S. Pat. No. 7,171,792 (Windahl et al.) discloses a pipe and cable truss system. Here, two inclined members are joined at an angle, forming the peak of the truss. Vertical members and tension cables are used to hold the structure together. In order to connect the tension cables, tabs with holes are attached to the rigid pipe members. These tabs, however, would not be adequate for high compression or out-of-plane loads. In addition, the use of tabs prohibits the attachment of tubes and rods in place of the tension cables.
Several companies offer joints for connecting tubes. Hy-Gain Corporation (Lincoln, Neb.) manufactures antenna support structures. Hy-Gain Model LJ-105CA contains a clamshell type joint that is used to connect multiple tubes inline and at 90 degree angles. Using these connectors, however, one is unable to attach tubes along the third axis. In addition, there is no means to connect compressional diagonal members through this type of joint. Cushcraft Corporation (Manchester, N.H.) also supplies clamshell type attachment joints for antenna support structures (Big Thunder Series); however, like with the Hy-Gain models, a single universal joint cannot be utilized to create an entire truss or frame.
AirDynamics Corporation (New York, N.Y.) provides fittings to connect carbon fiber tubes. These fittings are tube splices used by sliding one end into each tube. Adhesive is applied to the fitting prior to insertion within the tube, and the glue line lies between the outer periphery of the fitting and the inner tube wall.